1. Field of the Invention
The invention relates to a device for packaging a web roll with a packaging sheet and a packaging sheet dispenser and a method for packaging a web roll.
2. Background of the Invention
A device of this type is known based on German Patent GB 1 429 445. The web roll is wrapped therein with a plastic sheet which is so flexible that folds which might be created during the wrapping process do not present a problem. There is no interruption between the production of the body packaging and the production of the end packaging. The packaging sheet remains in one piece.
After the web roll is wrapped, it is sent to a furnace where the plastic sheet is shrink-wrapped. The sheet also shrinks on the faces, thereby covering them.
The use of a plastic sheet, however, is not environmentally friendly and should, thus, be viewed critically.
From the post-published DE 195 35 746 A1, a device is known that packages a web roll with a packaging sheet that consists of packing paper. In this device, the body packaging is produced by first guiding the packaging sheet in a helical line around the web roll. The packaging sheet is then severed and, in separate steps, an end packaging on both axial ends of the web roll is produced. An inner face cover can be placed in the projection created by the end packaging, and the axial projection is then wrapped on the end packaging. An outer face cover can then be attached to the wrapped axial projection, by, for example a packing press.
This procedure, however, is accompanied by certain difficulties. In conventional packaging devices, which work with a packaging sheet matching the width of the web roll, the web roll is placed in the center of the packaging device. That is, the axial center of the web roll is located equidistant from the two packing presses. When, at the end of the packaging process, the packing presses are moved toward the web roll, they arrive at the faces simultaneously. Thus, the axial forces exerted by the packing presses on the web roll simultaneously counteract one another.
This procedure leads to considerable problems in making a body packaging by a packaging sheet guided in a helical line. Even when the web roll is positioned in the center, it has been observed, in many cases, that one of the two packing presses reaches the web roll sooner than the other. This may be caused by a combination of two circumstances which result from the manufacture of a body packaging with a helical packaging sheet. First, the web roll temporarily has a larger--albeit only slightly--diameter on one axial end than on the other. Second, a relatively great number of rotations of the web roll are required to manufacture this type of body packaging. This leads to an axial migration of the web roll in the direction of the larger diameter. This migration can easily be in the vicinity of one or several centimeters. As the packing press arrives, it pushes the packaging sheet toward the other packing press with its normal speed. Thus, when the packing press meets the other packing press, a collision at twice the speed results. This impact can easily lead to a tearing of the packaging. In addition, a considerable wear and tear on the motor-drive of the first packing press results, because it must accelerate the entire weight of the web roll.